It is stressed that any theory of which it is claimed that it is compatible both with standard realism and with the experimental data is subject to severe constraints. One is that it must either incorporate superluminal influences or negate the free will of the experimentalist. The other one is that, in it. it is only at the price of accepting “backward causality” that a measurement can he interpreted as revealing the value the measured quantity had, just before, rather than (...) just after, the measurement look place. (shrink)

The idea is discussed according to which, in the Heisenberg picture, the operators correspond to the dynamic properties while the density matrix corresponds to our knowledge. A simple, soluble model is made use of in order to determine in what way this idea needs to be refined and what it then tells us about the relationship of reality and physics.

“To be” or “to be found”? Some contributions relative to this modern variant of Hamlet's question are presented here. They aim at better apprehending the differences between the points of view of the physicists who consider that present-day quantum measurement theories do reach their objective and those who deny they do. It is pointed out that these two groups have different interpretations of the verbs “to be” and “to have” and of the criterion for truth. These differences are made explicit. (...) A notion of “empirical reality” is constructed within the representation of which the physicists of the first named group can consistently uphold their claim. A detailed way of sharpening this definition so as to make empirical reality free of nonlocal actions at a distance is also described. (shrink)

ResumeLes avancées que la physique a effectuées au cours de notre siècle rendent intertables beaucoup des vues de la philosophie réaliste traditionnelle. Mais ce n'est pas à dire que la position réaliste, conçue au sens large, doive, ou même puisse, être abandonée. Le texte vise à montrer qu'il n'en est rien. Plus précisément il cherche àétablir que l'idée ? une réalité dont l'existence ne relève pas de l'esprit humain demeure une idée nécessaire, qu'il est même légitime de concevoir une telle (...) réalité comme entrevue gräce aux activités noétiques de l'homme, mais que cependant il semble aujourd'hui hautement présomptueux de concevoir les choses observées comme des éléments de la ≫réalité≫ dont il s'agit. Les phénomènes, qui sont l'objet de la physique, constituent cependant eux‐mêmes une réalité en un autre sens, puisqu'ils forment un ensemble doué? une forte structuration et ? une relative mais large autonomic par rapport à nous. La distinction proposée entre ≫réalité indépendante≪ ‐ dont ľ'existence ne reléve pas de l'homme ‐ et ≫réalité empirique≪ ‐ ou ensemble des phénoménes ‐ paraît done maintenant être une bonne clé pour l'intelligence du donné.SummaryThe advances of physics in this century have made a number of views of traditional realist philosophy untenable. But this is not to say that the ‘realist position, in the broad sense', must or even can be abandoned ‐ as it is the aim of this work to show. More specifically, the aim is to establish that the idea of ‘reality, the existence of which does not depend of the human mind', remains necessary, that one may even consider that the noetic activities of men let them catch a glimpse of the reality in question, but that today, however, it seems highly presumptuous to consider observed things as elements of the “reality” that we are concerned with here. Phenomena, which are the subject of physics, do however constitute a reality in another sense, since they form a whole endowed with structure and with a relative but extensive autonomy in relation to us. The proposed distinction between “independent reality” ‐ the existence of which does not depend on man ‐ and “empirical reality” ‐ or all phenomena taken together ‐ would therefore appear to be a good key to the understanding of raw data. (shrink)

Does physics describe anything that can meaningfully be called “independent reality,” or is it merely operational? Most physicists implicitly favor an intermediate standpoint, which takes quantum physics into account, but which nevertheless strongly holds fast to quite strictly realistic ideas about apparently “obvious facts” concerning the macro-objects. Part 1 of this article, which is a survey of recent measurement theories, shows that, when made explicit, the standpoint in question cannot be upheld. Part 2 brings forward a proposal for making minimal (...) changes to this standpoint in such a way as to remove such objections. The “empirical reality” thus constructed is a notion that, to some extent,does ultimately refer to the human means of apprehension and of data processing. It nevertheless cannot be said that it reduces to a mere name just labelling a “set of recipes that never fail.” It is shown that our usual notion of macroscopic causality must be endowed with similar features. (shrink)

Should we doubt the exactness of the predictive quantum rules of calculation? Although this question is sometimes raised in connection with the one on how to physically understand quantum mechanics, these two questions should not be mixed up. It is recalled here that even the first one is stil an object of controversy, and it is shown (a) that in one specific case the arguments put forward in support of such doubts are hardly cogent but (b) that, nevertheless, at least (...) in one specific other context, the question is worth attention. This is the problem of repeated imperfect measurements. Relative to it, a theoretical possibility is shown of discriminating between the thesis that the quantum rules are exact and a powerful theory of which it is proved that it cannot be reconciled with the assumption. (shrink)

With regard to the notion of cause—or more generally of influence—the various methods of proof of Bell's theorem do not all have the same bearing. The differences between two of these methods are analyzed, with regard to both their conceptual basis and their conclusions. It is shown that both methods give valuable information but, not too surprisingly, the one that is based on the more detailed and specific definition of the concept of influences, and that makes use of the concept (...) of attribute, leads to conclusions that are also to some extent more specific than those following from the other method. (shrink)